Advanced Bash-Scripting Guide

Really nice guide to shell scripting with bash.

"This tutorial assumes no previous knowledge of
scripting or programming, but progresses rapidly toward an
intermediate/advanced level of instruction . . . all
the while sneaking in little snippets of Unix wisdom and lore. It
serves as a textbook, a manual for self-study, and a reference and
source of knowledge on shell scripting techniques. The exercises
and heavily-commented examples invite active reader participation,
under the premise that the only way to really learn
scripting is to write scripts."